Power circuits, such as power inverters, are often used in a variety of high powered machinery. For example, new technology involving electric drives for high-powered, heavy machinery require powerful and robust power circuits. Such power circuits may include a plurality of transistors, such as insulated-gate bipolar transistors (IGBTs), which operate to perform the desired function of the circuit.
During operation, the transistors often become very hot, which necessitates the use of systems and methods for cooling the power circuit and/or individual transistors of the circuit. The circuit may be connected to, or otherwise be operatively associated with, a cooling system which may effectively draw heat away from the power circuit. An example of such a cooling system is a cold plate. Cold plates may include a variety of known cooling elements, such as fluid cooling channels. In an example cold plate for a power circuit as shown in U.S. Pat. No. 7,796,398 (“Method and Apparatus for Cooling Electronics”), a cold plate may include one or more heat pipes for drawing heat away from the circuit towards a heat sink.
However, during certain functions of a power circuit, overall cooling may not be sufficient. One such condition is a stall condition, which may occur when the power circuit is part of an electric drive for powering a heavy machine. A stall condition exists when a machine “stalls,” or ceases movement while in the middle of activity, but is still receiving power. For example, a track-type tractor may experience a stall condition when it is pushing a load that is too heavy for the drive; thusly, the machine's movement halts, or “stalls,” while the drive is still operating at a high power level. Machines operating during a stall condition may put heavy strain on power circuits associated with the machine's drive, often in the form of excessive heating of power circuit elements.
During a stall condition, the entire power circuit may not experience excessive heating, but rather, a small number of transistors and/or elements of the transistor (e.g., silicon dies which comprise an IGBT) may become excessively hot. Such excessive heating of elements of a power circuit may create “hot spots” on the circuit, where unacceptable temperatures exist. Hot spots may be damaging to a circuit and lead to a lower lifespan.